Conventional data center switches are typically built using packet switches. The packet switches are implemented with various electrical circuitry, such as Application Specific Integrated Circuits (ASICs). For example, a conventional packet switch providing 128×128 ports at 28 Gbps has each ASIC consuming about 150 W. For optical input/output, 4×28 G QSFP28 pluggable transceivers can be used, resulting in a 3.2 Tbps switch, excluding overhead. Another conventional switch is IBM's Torrent-based switch designed for high-performance computing. It uses packaged devices mounted on a ceramic substrate and a single packaged die. This configuration uses 28 optical Vertical Cavity Surface Emitting Lasers (VCSELs) transceivers each with 12 channels at 10 Gbps, for a total of 3.36 Tbps bandwidth. Various implementations focus on providing as large as possible switching capacity in a single ASIC, to improve overall network efficiency. Some conventional switching ASICs include the Tomahawk from Broadcom, which consumes close to 200 W of power for 32×100 GbE ports and the Spectrum from Mellanox, which consumes close to 135 W of power for 32×100 GbE ports.
Single Tbps switches and modules need to evolve to support orders of magnitude more bandwidth. One approach proposes the use of VCSELs and photodetectors (PD) directly attached to Complementary Metal-Oxide Semiconductor (CMOS) switching ASICs. This approach has a disadvantage of tightly coupling optical and electronic designs, i.e., a small change in one requires a complete redesign of the whole opto-electro-mechanical system. Also, this approach is likely limited to only using VCSELs and limits the number of implementable fiber connections (i.e., ports).
Data centers and the like require network interconnection between thousands of racks, and larger switching fabrics are built up in layers, using the aforementioned hardware. FIG. 1 illustrates a network diagram of a layered data center architecture. The various circles in the Spine and Pods are individual packet switches. As can be seen in FIG. 1, a large fraction of the individual switch ports is spent on internal interconnections for scaling, rather than for providing useful ports to servers. Note, various servers are shown in FIG. 1 connected to the bottom packet switches in the Pods. The power consumption associated with the ASICs and the links associated with these internal interconnections is excess. Stated differently, packet switching is not needed on these internal interconnections.
As such, one approach to streamlining the layered data center architecture is to replace the internal interconnections with all-optical switching. While all-optical switching has advantages of extremely low latency and reduction of optical transceivers, there are various disadvantages such as slow switching and quasi-static connections, increased link budgets from data center transceivers to accommodate switching loss (˜3 dB), limited port counts and limited optical cascading due to optical insertion loss, no visibility into digital signals for performance monitoring, label processing, and the like.